Colocalization of VACV and BMP-4 staining in brains of GBM xenografts. Successive paraffin-embedded tumor sections of a GLV-1h285 infected mouse brain implanted with GBM CSCs analyzed by immunohistochemistry, 98 days post injection of the virus. A) Detection of VACV structural protein, A27L for identification of areas of tumors infected with VACV. B) Detection of BMP-4 expression generated by GLV-1h285. Identification of both proteins in overlapping regions of the tumor is indicative of active BMP-4 production by GLV-1h285 in the GBM CSC xenograft brains.